To improve the finishing via a ceiling cornice between a door frame and a floor surface or a ceiling and facilitate execution by using a joint structure on the side of the entrance door of each room of a cabin.

The thickness of a door frame 2 is made nearly equal to the thickness of a wall panel 3 so that they are made nearly flush on both the surface and back face sides, and connecting recesses 3b, 3b are provided on both the surface and back face of the connecting edge section 3a of the wall panel 3 for connecting the door frame 2 and the wall panel 3. The connecting recesses 3b, 3b on both the surface and back face of the wall panel 3 are pinched by fin-like joint sections 2a, 2a provided on the door frame 2 side, or a single or multiple joint grooves are provided from the connection section side of the wall panel 3, and the fin-like joint sections 2a, 2a provided on the door frame 2 side are coupled with the joint grooves on the connection section side edge section of the wall panel 3.